The present invention relates to a tunnel boring machine, i.e. a machine by means of which a tunnel is bored to full area without using explosives.
It has long been a desire to be able to construct machines of the above mentioned kind for different tunnel diameters and thereby use module designs which are the same for the different tunnel diameters. Machines designed according to these ideas would be substantially cheaper because fewer parts need be specially designed for individual machines. Machines which comply with the above mentioned desire must have a driving shaft for the boring head which can stand the torque which the biggest machine requires. This gives a large diameter. At the same time the bearing adjacent to the boring head must admit passage, for instance for exchange of boring tools, in the smallest contemplated tunnel diameter.